Reject oversized messages without disconnecting the host (#6285)

* fix(client): reject a message over the daemon's size limit instead of reconnecting in a loop

The daemon closes the WebSocket with 1009 when a message exceeds its 100 MiB
limit. A workspace or agent creation that loses its connection mid-request
stays pending and, after reconnecting, finds no record of itself on the
daemon (the oversized frame was never read), so it resubmits the same frame
and the connection drops again every couple of seconds until the app reloads.

The client now checks each outbound frame against the same limit, which
protocol exports and the daemon sets explicitly, and fails that request with
a size error while the connection stays up.

Refs #5501

* test(client): cover the UTF-8 byte count at the message size limit

* fix(client): reject oversized relay messages without disconnecting

Check the encrypted wire size synchronously before submission, so a frame below the direct limit cannot close the relay and leave workspace creation resubmitting forever. Keep the relay limit shared with the existing checkout diff budget.

---------

Co-authored-by: paseo-bot[bot] <266920839+paseo-bot[bot]@users.noreply.github.com>

packages/client/src/daemon-client-relay-e2ee-transport.ts

@@ -1,3 +1,4 @@
+import { MAX_RELAY_WEBSOCKET_MESSAGE_BYTES } from "@getpaseo/protocol/websocket-message-limit";
 import {
   createClientChannel,
   type EncryptedChannel,
@@ -8,7 +9,11 @@ import type {
   DaemonTransportFactory,
   TransportLogger,
 } from "./daemon-client-transport-types.js";
-import { extractRelayMessage, normalizeTransportPayload } from "./daemon-client-transport-utils.js";
+import {
+  extractRelayMessage,
+  normalizeTransportPayload,
+  messageTooLargeError,
+} from "./daemon-client-transport-utils.js";
 
 type OpenHandler = () => void;
 type CloseHandler = (event?: unknown) => void;
@@ -137,7 +142,13 @@ export function createEncryptedTransport(
       if (!channel) {
         throw new Error("Encrypted channel not ready");
       }
-      void channel.send(normalizeTransportPayload(data)).catch((error) => {
+      const payload = normalizeTransportPayload(data);
+      // Reject synchronously so the requesting operation fails without closing the transport.
+      const wireBytes = channel.outboundWireByteLength(payload);
+      if (wireBytes > MAX_RELAY_WEBSOCKET_MESSAGE_BYTES) {
+        throw messageTooLargeError(wireBytes, MAX_RELAY_WEBSOCKET_MESSAGE_BYTES);
+      }
+      void channel.send(payload).catch((error) => {
         emitError(error);
       });
     },

packages/client/src/daemon-client-transport-utils.ts

@@ -133,3 +133,10 @@ export function encodeUtf8String(value: string): Uint8Array {
   }
   return out;
 }
+
+export function messageTooLargeError(size: number, limit: number): Error {
+  const toMiB = (bytes: number) => (bytes / (1024 * 1024)).toFixed(1);
+  return new Error(
+    `Message is too large to send (${toMiB(size)} MiB). The limit is ${toMiB(limit)} MiB, so send fewer or smaller attachments.`,
+  );
+}

packages/client/src/daemon-client.test.ts

@@ -7527,3 +7527,29 @@ test.each([false, true])(
     await send;
   },
 );
+
+test("measures an outbound message in UTF-8 bytes against the daemon's message limit", async () => {
+  const mock = createMockTransport();
+  const client = new DaemonClient({
+    url: "ws://test",
+    clientId: "message_limit_unit_test",
+    transportFactory: () => mock.transport,
+    reconnect: { enabled: false },
+  });
+  clients.push(client);
+  const connectPromise = client.connect();
+  mock.triggerOpen();
+  await connectPromise;
+  const mib = 1024 * 1024;
+
+  // "é" is one UTF-16 unit but two UTF-8 bytes, so this text is ~98 MiB on the wire.
+  void client.sendMessage("agent-1", "é".repeat(49 * mib)).catch(() => undefined);
+  expect(mock.sent).toHaveLength(1);
+
+  // ~60M characters is under the 100 MiB limit; ~120 MiB of UTF-8 is over it.
+  await expect(client.sendMessage("agent-1", "é".repeat(60 * mib))).rejects.toThrow(
+    "Message is too large to send (120.0 MiB). The limit is 100.0 MiB",
+  );
+  expect(mock.sent).toHaveLength(1);
+  expect(client.getConnectionState().status).toBe("connected");
+});

packages/client/src/daemon-client.ts

@@ -1,3 +1,4 @@
+import { messageTooLargeError } from "./daemon-client-transport-utils.js";
 import { legacyUsageIcon } from "./legacy-usage-icons.js";
 import { subscribeTimeline, type TimelineMessage } from "./timeline-subscription/index.js";
 import { ProviderSnapshotUpdates } from "./provider-snapshots/index.js";
@@ -13,6 +14,7 @@ import type { z } from "zod";
 import type { SessionEventSubscription } from "@getpaseo/protocol/messages";
 import type { ClientCapability } from "@getpaseo/protocol/client-capabilities";
 import type { AgentAttentionNotificationPayload } from "@getpaseo/protocol/agent-attention-notification";
+import { MAX_WEBSOCKET_MESSAGE_BYTES } from "@getpaseo/protocol/websocket-message-limit";
 import {
   AgentCreateFailedStatusPayloadSchema,
   AgentCreatedStatusPayloadSchema,
@@ -1132,6 +1134,19 @@ function getTransportFrameSize(frame: string | Uint8Array | ArrayBuffer): number
   return frame.byteLength;
 }
 
+function assertTransportFrameFits(frame: string | Uint8Array | ArrayBuffer): void {
+  if (typeof frame !== "string") {
+    if (frame.byteLength > MAX_WEBSOCKET_MESSAGE_BYTES)
+      throw messageTooLargeError(frame.byteLength, MAX_WEBSOCKET_MESSAGE_BYTES);
+    return;
+  }
+  // UTF-8 needs at most three bytes per UTF-16 unit, so only a string near the limit is measured.
+  if (frame.length * 3 <= MAX_WEBSOCKET_MESSAGE_BYTES) return;
+  const size = new TextEncoder().encode(frame).byteLength;
+  if (size > MAX_WEBSOCKET_MESSAGE_BYTES)
+    throw messageTooLargeError(size, MAX_WEBSOCKET_MESSAGE_BYTES);
+}
+
 function describeInboundTransportFrame(
   frame: unknown,
   rawBytes: Uint8Array | null,
@@ -1767,6 +1782,8 @@ export class DaemonClient {
     if (!this.transport) {
       throw new DaemonConnectionError("Transport not connected");
     }
+    // The daemon closes the connection on an oversized message, and creations resubmit on reconnect.
+    assertTransportFrameFits(frame);
     const isOpen = this.beginTraceSection("paseo.ws.frame.outbound", {
       kind: typeof frame === "string" ? "text" : "binary",
       size: String(getTransportFrameSize(frame)),

packages/protocol/src/websocket-message-limit.ts

@@ -0,0 +1,5 @@
+/** Largest WebSocket message the daemon accepts. A bigger one closes the connection with 1009. */
+export const MAX_WEBSOCKET_MESSAGE_BYTES = 100 * 1024 * 1024;
+
+/** Largest encrypted frame the relay accepts. */
+export const MAX_RELAY_WEBSOCKET_MESSAGE_BYTES = 32 * 1024 * 1024;

packages/server/package.json

@@ -89,7 +89,7 @@
     "speech:transcribe:local": "tsx scripts/transcribe-local-wav.ts",
     "test": "npm run test:unit && npm run test:integration",
     "test:unit": "vitest run --fileParallelism --exclude \"**/*.e2e.test.ts\"",
-    "test:integration": "vitest run --maxWorkers=1 src/server/daemon-e2e/filesystem.e2e.test.ts src/server/daemon-e2e/file-download.e2e.test.ts src/server/daemon-e2e/cli-logs-follow.e2e.test.ts src/server/creation/creation.e2e.test.ts src/server/daemon-e2e/terminal-workspace-sdk.e2e.test.ts src/server/daemon-e2e/models.e2e.test.ts src/server/daemon-e2e/live-preferences.e2e.test.ts src/server/agent/model-catalog.e2e.test.ts src/server/plugins/plugin-paseo-api.e2e.test.ts && vitest run --maxWorkers=1 src/server/daemon-e2e/git-operations.e2e.test.ts -t \"merges into\" && vitest run --maxWorkers=1 src/server/session.create-agent-worktree-autoarchive.e2e.test.ts -t \"creates a worktree and auto-archives both\" && vitest run --maxWorkers=1 src/server/agent/providers/opencode-bridge.local.e2e.test.ts -t \"versioned runtime\"",
+    "test:integration": "vitest run --maxWorkers=1 src/server/daemon-e2e/filesystem.e2e.test.ts src/server/daemon-e2e/file-download.e2e.test.ts src/server/daemon-e2e/cli-logs-follow.e2e.test.ts src/server/creation/creation.e2e.test.ts src/server/daemon-e2e/terminal-workspace-sdk.e2e.test.ts src/server/daemon-e2e/models.e2e.test.ts src/server/daemon-e2e/live-preferences.e2e.test.ts src/server/daemon-e2e/oversized-message.e2e.test.ts src/server/agent/model-catalog.e2e.test.ts src/server/plugins/plugin-paseo-api.e2e.test.ts && vitest run --maxWorkers=1 src/server/daemon-e2e/git-operations.e2e.test.ts -t \"merges into\" && vitest run --maxWorkers=1 src/server/session.create-agent-worktree-autoarchive.e2e.test.ts -t \"creates a worktree and auto-archives both\" && vitest run --maxWorkers=1 src/server/agent/providers/opencode-bridge.local.e2e.test.ts -t \"versioned runtime\" && vitest run --maxWorkers=1 src/server/daemon-e2e/relay-transport.e2e.test.ts -t \"oversized attachments\"",
     "test:hub-cli-contract": "vitest run --maxWorkers=1 src/server/hub/hub-cli-contract.test.ts",
     "test:integration:all": "npm run test:e2e",
     "test:integration:real": "vitest run real.e2e.test.ts",

packages/server/src/server/daemon-e2e/oversized-message.e2e.test.ts

@@ -0,0 +1,58 @@
+import { describe, test, expect, beforeEach, afterEach } from "vitest";
+import { mkdtempSync, rmSync } from "fs";
+import { tmpdir } from "os";
+import path from "path";
+import { createDaemonTestContext, type DaemonTestContext } from "../test-utils/index.js";
+
+let ctx: DaemonTestContext;
+let cwd: string;
+
+beforeEach(async () => {
+  ctx = await createDaemonTestContext();
+  cwd = mkdtempSync(path.join(tmpdir(), "daemon-e2e-"));
+});
+
+afterEach(async () => {
+  await ctx.cleanup();
+  rmSync(cwd, { recursive: true, force: true });
+}, 60000);
+
+describe("a message larger than the daemon accepts", () => {
+  const oversizedImage = { data: "A".repeat(101 * 1024 * 1024), mimeType: "image/png" };
+
+  test("fails the creation and keeps the connection up", async () => {
+    const statuses: string[] = [];
+    const unsubscribe = ctx.client.subscribeConnectionStatus((state) => {
+      statuses.push(state.status);
+    });
+
+    await expect(
+      ctx.client.createAgent({
+        provider: "claude",
+        cwd,
+        title: "Oversized first message",
+        initialPrompt: "Describe these screens.",
+        images: [oversizedImage],
+      }),
+    ).rejects.toThrow(/too large/);
+    unsubscribe();
+
+    expect(statuses).toEqual(["connected"]);
+    expect((await ctx.client.fetchAgents()).entries).toEqual([]);
+  }, 30000);
+
+  test("fails the send and keeps the connection up", async () => {
+    const agent = await ctx.client.createAgent({ provider: "claude", cwd, title: "Agent" });
+    const statuses: string[] = [];
+    const unsubscribe = ctx.client.subscribeConnectionStatus((state) => {
+      statuses.push(state.status);
+    });
+
+    await expect(
+      ctx.client.sendMessage(agent.id, "Describe these screens.", { images: [oversizedImage] }),
+    ).rejects.toThrow(/too large/);
+    unsubscribe();
+
+    expect(statuses).toEqual(["connected"]);
+  }, 30000);
+});

packages/server/src/server/daemon-e2e/relay-transport.e2e.test.ts

@@ -1,4 +1,6 @@
 import { describe, expect, test } from "vitest";
+import { withTimeout } from "../../utils/promise-timeout.js";
+import { DaemonClient } from "../test-utils/daemon-client.js";
 import { WebSocket } from "ws";
 import pino from "pino";
 import { Writable } from "node:stream";
@@ -202,12 +204,20 @@ async function waitForCapturedLog(
     if (options.useLocalRelay) {
       relayArgs.push("--var", "PASEO_RELAY_UPSTREAM:");
     }
-    relayProcess = spawn("npx", relayArgs, {
-      cwd: relayDir,
-      env: { ...process.env },
-      stdio: ["ignore", "pipe", "pipe"],
-      detached: false,
-    });
+    relayProcess = spawn(
+      process.execPath,
+      [
+        "--experimental-vm-modules",
+        path.resolve(relayDir, "../../node_modules/wrangler/wrangler-dist/cli.js"),
+        ...relayArgs.slice(1),
+      ],
+      {
+        cwd: relayDir,
+        env: { ...process.env },
+        stdio: ["ignore", "pipe", "pipe"],
+        detached: false,
+      },
+    );
 
     relayProcess.stdout?.on("data", (data: Buffer) => {
       const lines = data
@@ -241,6 +251,73 @@ async function waitForCapturedLog(
     relayProcess = null;
   };
 
+  test("oversized attachments fail without disconnecting or resubmitting over the relay", async () => {
+    await startRelay({ useLocalRelay: true });
+    const daemon = await createTestPaseoDaemon({
+      relayEnabled: true,
+      relayEndpoint: `127.0.0.1:${relayPort}`,
+      relayUseTls: false,
+      relayPublicUseTls: false,
+    });
+    let client: DaemonClient | null = null;
+    try {
+      const offerUrl = await getPairingOfferUrl({
+        paseoHome: daemon.paseoHome,
+        relayEnabled: true,
+        relayEndpoint: daemon.config.relayEndpoint,
+      });
+      const { serverId, daemonPublicKeyB64 } = decodeOfferFromFragmentUrl(offerUrl);
+      client = new DaemonClient({
+        url: buildRelayWebSocketUrl({
+          endpoint: `127.0.0.1:${relayPort}`,
+          useTls: false,
+          serverId,
+          role: "client",
+        }),
+        e2ee: { enabled: true, daemonPublicKeyB64 },
+        reconnect: { baseDelayMs: 100, maxDelayMs: 100 },
+      });
+      await client.connect();
+      const statuses: string[] = [];
+      client.subscribeConnectionStatus((state) => statuses.push(state.status));
+      for (const imageMiB of [30, 61]) {
+        // Attachments are base64 in the JSON, then E2EE base64 expands the frame again.
+        const images = [
+          { data: "A".repeat(4 * Math.ceil((imageMiB * 1024 * 1024) / 3)), mimeType: "image/png" },
+        ];
+        await expect(
+          withTimeout(
+            client.createWorkspace({
+              source: { kind: "directory", path: daemon.staticDir },
+              agent: {
+                provider: "claude",
+                cwd: daemon.staticDir,
+                initialPrompt: "Describe these screens.",
+                images,
+              },
+            }),
+            10000,
+            "Workspace creation did not settle",
+          ),
+        ).rejects.toThrow(/too large.*32\.0 MiB/);
+        expect((await client.fetchAgents()).entries).toEqual([]);
+      }
+      const agent = await client.createAgent({ provider: "claude", cwd: daemon.staticDir });
+      await expect(
+        client.sendMessage(agent.id, "Describe these screens.", {
+          images: [{ data: "A".repeat(40 * 1024 * 1024), mimeType: "image/png" }],
+        }),
+      ).rejects.toThrow(/too large.*32\.0 MiB/);
+      await client.sendMessage(agent.id, "A small follow-up still works.");
+      expect((await client.fetchAgents()).entries).toHaveLength(1);
+      expect(statuses).toEqual(["connected"]);
+    } finally {
+      await client?.close();
+      await daemon.close();
+      await stopRelay();
+    }
+  }, 60000);
+
   test("daemon connects to relay and client ping/pong works through relay", async () => {
     process.env.PASEO_PRIMARY_LAN_IP = "192.168.1.12";
 

packages/server/src/server/websocket-server.ts

@@ -33,6 +33,7 @@ import {
 } from "./messages.js";
 import { asUint8Array, decodeBinaryFrame } from "@getpaseo/protocol/binary-frames/index";
 import type { TerminalActivity } from "@getpaseo/protocol/terminal-activity";
+import { MAX_WEBSOCKET_MESSAGE_BYTES } from "@getpaseo/protocol/websocket-message-limit";
 import type { HostnamesConfig } from "./hostnames.js";
 import { isHostnameAllowed } from "./hostnames.js";
 import {
@@ -822,6 +823,7 @@ export class VoiceAssistantWebSocketServer {
     const wss = new WebSocketServer({
       server,
       path: "/ws",
+      maxPayload: MAX_WEBSOCKET_MESSAGE_BYTES,
       handleProtocols: (protocols) => selectWebSocketProtocol(protocols, password),
       verifyClient: ({ req }, callback) => {
         this.verifyWsUpgrade(

packages/server/src/utils/checkout-git.ts

@@ -1,3 +1,4 @@
+import { MAX_RELAY_WEBSOCKET_MESSAGE_BYTES } from "@getpaseo/protocol/websocket-message-limit";
 import { resolve, dirname, basename } from "path";
 import { existsSync, realpathSync } from "fs";
 import { open as openFile, readFile, stat as statFile } from "fs/promises";
@@ -2152,13 +2153,13 @@ export async function getCheckoutSnapshotFacts(
 
 const PER_FILE_DIFF_MAX_BYTES = 1024 * 1024; // 1MB
 const TOTAL_DIFF_MAX_BYTES = 2 * 1024 * 1024; // 2MB
-const RELAY_MAX_FRAME_BYTES = 32 * 1024 * 1024;
 const CHECKOUT_DIFF_FRAME_HEADROOM_BYTES = 1024 * 1024;
 // Temporary until diffs load lazily per file. The Paseo relay's 32 MiB frame limit is
 // binding: string frames are encrypted and base64-encoded. Reserve 1 MiB plaintext for
 // the surrounding WebSocket JSON envelope after inverting that exact wire expansion.
 export const CHECKOUT_DIFF_MAX_STRUCTURED_BYTES =
-  maxBase64EncryptedPlaintextByteLength(RELAY_MAX_FRAME_BYTES) - CHECKOUT_DIFF_FRAME_HEADROOM_BYTES;
+  maxBase64EncryptedPlaintextByteLength(MAX_RELAY_WEBSOCKET_MESSAGE_BYTES) -
+  CHECKOUT_DIFF_FRAME_HEADROOM_BYTES;
 
 interface StructuredDiffAccumulator {
   files: ParsedDiffFile[];